1. Field of the Invention
The present invention relates to an optical device.
2. Description of Related Art
A half-mirror that can adjust the reflectance by using dielectric multilayer films is conventionally known (for example, see Japanese Unexamined Patent Application, Publication No. Sho-64-72102). Further, a anti-reflection technology by using multilayer films is also known (for example, see Japanese Unexamined Patent Application, Publication No. 2003-98312).
In these cases, the reflectance is accurately controlled with multilayer films by adjusting the thickness and the refractive index of each layer of the multilayer films.
However, in the case of the multilayer films described in Japanese Unexamined Patent Application, Publication No. Sho-64-72102 and Japanese Unexamined Patent Application, Publication No. 2003-98312, it is difficult to change the thickness and the refractive index of each layer of the multilayer films toward an in-plane direction that is perpendicular to the thickness direction in each layer. As a result, it is difficult to configure an optical device in which refractive power is accurately controlled with multilayer films.